1. Field of the Invention
The present invention relates to reflectors for vehicular lamps, and is intended to provide a novel reflector for a vehicular lamp which can improve the lamp appearance and light distribution. The reflector avoids significant level differences at boundaries between reflecting sections, which originate from the division of the reflecting surface into reflecting sections in order to form a reflecting surface that conforms to a vehicle body shape. The invention further relates to a method of producing a die for such a reflector.
2. Description of the Background Art
As a recent trend, rounded or streamlined vehicle body shapes are employed to satisfy the requirements for styling of vehicles in view of aerodynamic characteristics and design. It is necessary for a lamp shape to be designed, i.e., curved or inclined to the vertical direction, so as to conform to an external shape of a vehicle.
Influenced by this design trend, the design of reflecting surfaces cannot be limited to a single paraboloid of revolution. With a further trend of shifting the light distribution control function, which previously had been assigned to an outer lens, to a reflector, the reflecting surface is constituted, for instance, as a composite reflecting surface that is a combination of a plurality of paraboloids of revolution or very small reflecting surfaces.
As an example of such a design trend, FIG. 11 shows an appearance of a tail and stop lamp a of a vehicle, in which a stop lamp portion b and a turn signal lamp portion c are combined to form an integral part.
An outer lens e attached to a lamp body d has a shape in which the degree of its curve increases towards the corner of the vehicle, and which is slightly inclined with respect to the vertical direction.
FIG. 12 shows the main part of a reflector.
Like the outer lens e, which is designed to conform to the vehicle body shape, a reflector f consists of two reflecting portions g, g that are connected to each other so as to conform to the vehicle body shape. Reflecting surfaces h, h are formed by subjecting part of the lamp body d to a reflection treatment, i.e., evaporation.
Each reflecting surface h is divided into two parabolic reflecting sections i, i having different focal lengths.
Reference characters j, j denote bulb insertion holes formed at the centers of the respective reflecting portions g, g.
As long as the fundamental surface of the reflecting surface h is a curved surface that can be expressed as an analytical function like a paraboloid of revolution, it is difficult to obtain a shape that can freely accommodate various vehicle body shapes. As a result, level differences k, k are formed at the boundary between the reflecting sections i, i, i.e., at the connecting portions of the reflecting sections i, i that are located over and under the bulb insertion hole j.
FIG. 13 shows part of an inner lens l as disposed in the lamp. Several cylindrical lens steps n, n, . . . extending in the horizontal direction are formed on the back surface of a bottom portion m of the inner lens l, and fisheye steps q, q, . . . are formed on the back surface of an upper portion o.
In the lamp a as described above, the level differences k, k at the boundary between the reflecting sections i, i will cause a problem in that the lamp appearance is deteriorated by the level differences k, k seen through the outer lens e while the lamp a is turned on.
In particular, this phenomenon is conspicuous at the part of the level differences k that correspond to the bottom portion m of the inner lens l. Specifically, at that part, as indicated by circles of a broken line in FIG. 11, dark streaks s corresponding to the level differences k appear on the surface of the outer lens e and are very noticeable.
To solve the above problem, various methods are used conventionally. For example, to avoid formation of the level differences, one may forcibly design the reflecting surface h as a smooth surface while recognizing a possibility that the lower half of the reflecting surface h may deviate from a paraboloid surface. Alternatively, the surface at the level difference may be made a slanting surface, or the inner lens l may be subjected to roughening (e.g., sandblasting). However, either method is an individual measure, and cannot be the best method because eventually an influence (i.e., scattered light by the surface at the level difference or the roughened surface) on the light distribution control should be considered.